This study will assess the sensitivity and specificity of prenatal ultrasound performed between 13 and 28 weeks of gestation to detect approximately 38 different structural malformations of the fetus. Currently, there is little available evidence concerning these detection rates in the community setting. Thus, this information will be of immediate use to physicians and pregnant women, assisting them in making informed choices concerning; 1) the usefulness of routine prenatal ultrasound examinations 2) the accuracy of ultrasound examinations that are negative for congenital anomalies and 3) the accuracy of ultrasound examinations that are positive for congenital anomalies. We plan to create a multi-ethnic cohort of 76,000 women who had prenatal ultrasound exams at the University of Texas Medical School at Houston between 1998 and 2006. Computerized records of ultrasound examinations will be linked with birth certificates and fetal death certificates. They will also be linked with records of the Texas Birth Defects Registry, an active, population based registry, administered by the Texas Department of State Health Services. The proposed study will include an estimated 1,450 infants with structural malformations. This will be one of the most statistically powerful studies of the ability of prenatal ultrasound to detect congenital anomalies. Estimates of sensitivity and specificity will be calculated for each of 38 different categories of malformations. [unreadable] [unreadable] [unreadable]